Two years age my 24x24 was approx $8000, I did everything myself with some help from friends.
Including: 24'x24'x6" slab w/#5 rebar 16" oc each way, 9' side walls, trusses, roofing, aluminum facia-soffits-gutters, wood siding, house wrap, all 5/8" osb roof and walls, 16x7 overhead door, 3'...